In recent years, studies and developments have been advanced regarding size increase of a display panel using organic EL elements. The organic EL element has a structure in which a light emitting layer composed of an organic compound is sandwiched by one pair of electrodes. The film thickness of this light emitting layer correlates with the light emission luminance and it is desirable that the film thickness in the pixel region of the display panel be even. For size increase of the display panel, many studies have been made on a method for uniformizing the film thickness of the light emitting layer in this pixel region.
Methods for forming the light emitting layer are roughly categorized into dry processes such as a vacuum evaporation method and wet processes such as an inkjet method. The wet processes are considered as techniques suitable for size increase of the display panel from the aspect of the formation accuracy thereof and the cost.
In the case of forming the light emitting layer by the wet process, generally partition walls (banks) are formed over a substrate in advance and the light emitting layer is formed in the pixel regions marked out by the partition walls. As the partition walls, there are two kinds of partition walls: pixel banks obtained by forming partition walls in a lattice manner and line banks obtained by forming plural streaks of partition walls extending along the column direction (for example, refer to PTL 1).
In the case of the line banks, a solution containing an organic compound serving as the material of the light emitting layer (hereinafter, referred to as “ink”) can flow in the column direction in the gap between the partition walls. Thus, even when the amount of application of the ink varies in the column direction, film thickness unevenness among the pixel regions can be reduced due to the subsequent ink flow.
Incidentally, the ink generally has high surface tension. Therefore, if a foreign matter and a mass of ink whose drying has proceeded exist in the gap between the partition walls, the ink easily concentrates at the places where they exist. In particular, in the case of the line banks, because the ink can flow in the column direction, the ink easily concentrates from a wide range at the places where the foreign matter and the mass of ink exist and possibly large film thickness unevenness occurs in the column direction (refer to PTL 2).
Therefore, in an organic EL display panel of PTL 2, as shown in FIG. 14, in addition to plural streaks of first partition walls 916 extending along the column direction, plural streaks of second partition walls 914 extending along the row direction are further formed. Due to the formation of the second partition walls 914, the flow of ink applied to gaps 920 between the adjacent first partition walls 916 in the column direction is moderately suppressed and thus the ink concentrates less readily from a wide range at places where a foreign matter and a mass of ink exist. As a result, the occurrence of film thickness unevenness in the column direction is suppressed.